An All Oxide α-Fe2O3/H:TiO2 Heterojunction Photoanode: A Platform for Stable and Enhanced Photoelectrochemical Performance through Favourable Band Edge Alignment

To improve the photoelectrochemical performance of hematite thin film photoanode, we report a novel heterostructure based on Fe2O3/TiO2 and hydrogenated Fe2O3/TiO2 (Fe2O3/H:TiO2) for faster charge transfer owing to passivation of surface states in Fe2O3 via TiO2 overlayer and favourable band alignment using hydrogen annealing of TiO2 overlayer. The valence band offset, band gap and work-function values have been measured using X-ray photoelectron spectroscopy (XPS), optical absorption, Kelvin probe force microscopy (KPFM) to construct the energy band diagram of the heterostructure photoanodes. The results confirm the upshift in the valence band edge of TiO2 over Fe2O3 after hydrogen treatment of TiO2 overlayer which leads to formation of type-II band edge alignment in Fe2O3/H:TiO2 heterojunction and improved PEC performance compared to that of the Fe2O3/TiO2, pristine Fe2O3 and TiO2 thin film photoelectrodes. The well straddled and improved band alignment in Fe2O3/H:TiO2 heterostructure gives rise to subs...